1. Field of the Invention
The present invention relates to an image forming apparatus and more particularly to an image forming apparatus comprising an image forming machine, such as an electrophotographic machine and a laser printer, and a sorter with a sheet binding function.
2. Description of Related Art
In the art of copying machine and printer for forming images on sheets, there have been developed various sorters with automatic staplers. Generally, a cartridge method is adopted in loading such automatic staplers with binding elements (staples). A sensor for detecting staples is provided in such an automatic stapler, and when the sensor detects that the number of staples in the stapler becomes less than a certain number, the apparatus is controlled so as to indicate emptiness of the stapler, to stop the operation and to instruct loading of staples. This type of apparatus is disclosed in U.S. Pat. No. 4,864,350.
However, in a sorter where a stapler moves within a case intermittently along bins so as to staple sheets distributed to each bin, emptiness of the stapler during a stapling operation causes the following problems. When the stapler stops in the middle of the case, loading of staples is difficult. In order to comply with this situation, the case must be openable entirely and must be mechanically strong, which is expensive. With a conventional sorter, an operator cannot recognize the number of remaining staples, and when the operator designates a number larger than the number of remaining staples as the number of copy sets, the operation will be discontinued.
In the art of sorter with a sheet binding function, speedy sheet distribution and speedy sheet binding are most demanded. Accordingly, a reciprocating sorting method is adopted in distributing sheets among bins. Specifically, distribution of copies of a first original begins with a bin at an end and proceeds toward a bin at the other end, and distribution of copies of a next original reverses the bins. However, there have been no techniques to speed up sheet binding.